Monitoring wells installed as part of groundwater investigations related to leaking surface or underground storage tanks are typically constructed of two or four inch diameter PVC casing and well screen to between 20 to 100+ feet depending on the depth to groundwater. The protocol for taking water samples from these monitoring wells requires that the well be pumped or bailed until three to five well volumes have been removed, the well dewaters, or successive measures of indicator parameters pH, temperature, and electrical conductivity have stabilized.
For water level depths less than about 25 feet an electric surface suction pump and an inwell purge tube is often used to pump the well. The inwell purge tube has a check valve at is bottom so that rapid up and down motion of the purge tube will fill the tube with water and allow the surface suction pump to be primed. Once the surface suctions pump is primed, the pump will deliver water from the well until the water level declines to a theoretical limit of about 30 feet below the suction pump depending on ambient atmospheric pressure (14.7 psi=33.9 feet). As the water level depth increases due to pumping, the flow rate declines because of the increased lift required. Flow rates up to 3 gallons per minute are attainable with surface suction pumps.
For water level depths greater than about 25 feet, small electric submersible pumps or compressed air (or nitrogen) displacement pumps designed for 2 or 4 inch diameter wells are used to purge monitoring wells. These pumps push water from inside the well to the surface through attached tubing and require downhole electrical or air lines to activate the pump. The flow rate of these downhole pumps rarely exceeds 2 gpm.
The inventor routinely purges 2″ diameter monitoring wells where the water level depth is less than 25 feet with a 12 volt surface suction pump connected to dedicated (stays in the well) purge tube having a bottom check valve. The impetus for this invention was the effort required to purge some monitoring wells where the water level depths were greater than about 25 feet and where the flow rate of the surface suction pump was very low or zero. In these situations the inventor would purge the wells by hand by rapidly jacking the purge tube up and down until the requisite three to five well bore volumes were pumped from the well.
The invention provides a means of translating rotary motion in the horizontal plane, such as provided by a portable hand drill, to rapid, cyclic, up and down motion of a well pump tube so that the well can be pumped from any depth without placing a pump in the well. The present embodiment of the invention can pump a constant 2.5 gallons per minute from a 2 inch diameter monitoring well regardless of the water level depth or changes in the water level depth.
Other applications of the rotary-to-linear motion translater described herein are given in the claims section below.